[RFC] netrw: Remove NetReadFixup()

While removing Win95 references I found this function, which describes itself like so:

```
This sort of function is typically written by the user to handle extra junk
that their system's ftp dumps into the transfer. This function is provided as
an example and as a fix for a Windows 95 problem: in my experience, win95's ftp
always dumped four blank lines at the end of the transfer.
```

Of course this could still be useful, but having searched for its usage I'm not too
confident it's even applicable anymore. If anyone actually uses it please say so.